Electron discharge devices



March 5, 1957 R. B. COULSON ELECTRON DISCHARGE DEVICES Filed March 23, 1953 United States Patent 9 ELECTRON DISCHARGE DEVICES Robert Bernard Coulson, Chelmsford, England, assignor to English Electric Valve Company Limited, London, England, a British company Application March 23, 1953, Serial No. 343,984 Claims priority, application Great Britain April 29, 1952 1 Claim. (Cl. 3153.5)

This invention relates to electron discharge tubes and more specifically to such tubes of the so-ca'lled travelling wave tube type in which there is a winding, usually helical, which in use acts as a delay line carrying a wave which interacts with an electron beam which is projected axially through the winding to a collector.

It is very important in such travelling wave tubes which will hereinafter be termed travelling wave tubes of the co-axial beam and winding type-to support the winding firmly and accurately in predetermined position with respect to the beam. Numerous expedients have been used in the past for satisfying this requirement and the winding has been supported from the envelope by clip and supports of various kinds. However, the known proposals have been found to have one or more of the disadvantages of cost, complexity, difficulty of assembly and lack of accuracy and rigidity of support. The present invention seeks to provide improved travelling wave tubes of the co-axial beam and winding type which shall have none of these disadvantages and shall be moreover such as to be well adapted for repetition production.

According to this invention a travelling wave tube of the co-axial beam and winding type is provided with an envelope of triangular internal cross-section and the winding is supported in predetermined position in that crosssection by means, of three insulating support rods which lie in the corners of the section and support the said winding from the envelope by contacting with the internal wall of the envelope at the corners of the internal section thereof and also contacting with the winding at interrupted lines of contact extending over substantially its whole length.

The invention has the advantage that no clips or fastening means are necessary while the members concernednamely the winding itself and the three support rodswhen placed in their proper positions will retain those positions by virtue only of their shapes and dimensions. Moreover, the three support rods support the winding at every turn thereof i. e. in interrupted line of contact running substantially the whole length of the winding.

The terms triangular and corners are used in this specification in a wide sense to refer also to shapes which are not strictly triangular but approximately so e. g. modified triangular with truncated or flattened corners.

Preferably the support rods are circular sectioned straight support rods running parallel to the axis of a helical winding and the triangular sectioned envelope is a simple straight envelope of the said section.

Preferably also the triangular section is equilateral, the interrupted lines of contact with the winding being at 120 to one another.

turns of the helix.

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The invention is illustrated in the single figure of the accompanying drawing, which shows in cross sectional view one embodiment thereof so far as is necessary to an understanding of the said invention. Parts of the tube not concerned wit-h this invention are not shown.

Referring to the drawing the tube has an envelope 1 which is made of glass and has an internal section of equilateral triangular shape, the corners of the triangle being flattened or truncated as shown at 2. The figure represents the section of the envelope taken at any point in its length. A beam of electrons is projected along the median axes 7 of the equilateral triangle constituted by the envelope 1. The beam of electrons is propagated from an electron beam source indicated at 8 in the draw ing whereby the beam of electrons may be projected along the aforesaid median axe 7. Centrally within the envelope is a helical winding 3 which is supported in position by three silica, glass or ceramic rods 4 of circular section. There is one red 4 in each corner. The diameters of the said rods and of the helix are so chosen that when assembled the part-s maintain themselves in the position shown in the drawing there being interrupted line contacts between the rods and the winding and line contacts between the rods and the internal wall of the envelope. More specifically the rods 4 contact with the internal walls of the envelope at continuous lines 5 and with the helix 3 at interrupted lines 6, the interruptions of course occurring at the spaces between the successive The rods 4 run substantially the whole "length of the helix and thu provide firm and accurate support over its whole length. As will be seen the tube envelope is of an extremely strong shape and can readily be made of a high degree of straightness so that the helix is accurately and firmly positioned.

Iclaim:

A travelling wave tube comprising an elongated evacuated envelope of substantially equilateral triangular internal cross section, said envelope containing an electron beam source adapted to project a beam of electrons along the medium axis of said equilateral triangle, a helical winding coaxial with said median axis and extending along the length thereof, and three insulating support rods of circular section and positioned one in each corner of said triangle, said rods being of substantially the same diameter, and the common diameter of said rods and the diameter of said helical winding being .so chosen that each of said rods is tangential to two adjacent ides of said triangle and to said winding, the lines of contact between said rods and said winding being substantially equally spaced around said winding, and in which each interior corner of the equilateral triangle constituting the envelope is flattened providing pockets which receive said support rods, the surfaces of the rods which are opposite to the spaced contacts between said rods and said winding being tangent to the flattened interior corners of said envelope.

References Cited in the file of this patent UNITED STATES PATENTS 2,602,148 Pierce July 1, 1952 2,730,649 Dewey Jan. 10, 1956 FOREIGN PATENTS 984,595 France Feb. 28, 1951 664,663 Great Britain Jan. 9, 1952 

